A belt-type continuously variable transmission has hitherto been well known as one of continuously variable transmissions for vehicles. This belt-type continuously variable transmission includes a primary pulley and a secondary pulley on respective rotation axes disposed in parallel with each other and a transmission belt is wound around the both pulleys to transmit power. Each of the primary and secondary pulleys is made up mainly of a fixed sheave and a movable sheave and the movable sheave is moved relatively to the rotation axis in the axial direction to change a groove width formed between the fixed sheave and the movable sheave. A change in the groove width varies a winding position of the transmission belt, i.e., a winding radius of the transmission belt and, therefore, a gear ratio of the belt-type continuously variable transmission is continuously varied. For example, belt-type continuously variable transmissions of Patent Documents 1 to 3 are examples thereof. The basic configuration of the belt-type continuously variable transmissions of Patent Documents 1 to 3 will be described with reference to a cross-sectional view of a belt-type continuously variable transmission 600 depicted in FIG. 16.
As depicted in FIG. 16, the belt-type continuously variable transmission 600 mainly includes an input shaft 604 and an output shaft 606 disposed in parallel with each other in a case 602, a primary pulley 608 disposed on the side of the input shaft 604, a secondary pulley 610 disposed on the side of the output shaft 606, and a transmission belt 612 wound between the primary pulley 608 and the secondary pulley 610.
The input shaft 604 is disposed side-by-side with a torque converter 614 and a forward/reverse switching mechanism 616 on the same axial center C1 and rotation of an engine not depicted is transmitted via the torque converter 614 and the forward/reverse switching mechanism 616.
The primary pulley 608 is made up of a disc-shaped fixed sheave 618 formed integrally with an outer circumferential portion of the input shaft 604 and a movable sheave 620 spline-fitted relatively non-rotatably and relatively movably in the axial direction to the input shaft 604 with a V-groove 622 formed between the fixed sheave 618 and the movable sheave 620. The V-groove 622 is changed in groove width by relatively moving the movable sheave 620 in the axial direction by a hydraulic actuator 623. FIG. 16 depicts a state of the V-groove 622 with the widest groove width, i.e., a state of the belt-type continuously variable transmission 600 with the maximum gear ratio γmax on the upper side relative to the axial center C1 of the primary pulley 608 and the narrowest state of the V-groove 622, i.e., a state of the belt-type continuously variable transmission 600 with the minimum gear ratio γmin on the lower side relative to the axial center C1 of the primary pulley 608.
The secondary pulley 610 is made up of a disc-shaped fixed sheave 624 formed integrally with an outer circumferential portion of the output shaft 606 and a movable sheave 626 spline-fitted relatively non-rotatably and relatively movably in the axial direction to the output shaft 606 with a V-groove 628 formed between the fixed sheave 624 and the movable sheave 626. The V-groove 628 is changed in groove width by relatively moving the movable sheave 626 in the axial direction by a hydraulic actuator 630. FIG. 16 depicts the widest state of the V-groove 628, i.e., the state of the belt-type continuously variable transmission 600 with the minimum gear ratio γmin on the upper side relative to the axial center C2 of the secondary pulley 610 and the narrowest state of the V-groove 628, i.e., the state of the belt-type continuously variable transmission 600 with the maximum gear ratio γmax on the lower side relative to the axial center C2 of the secondary pulley 610.
The transmission belt 612 is wound between the V-groove 622 formed in the primary pulley 608 and the V-groove 628 formed in the secondary pulley 610, and a change in the groove widths of the respective V-grooves 622 and 628 varies a winding position, i.e., a winding radius of the transmission belt 612.
Thus, in the belt-type continuously variable transmission 600, the movable sheaves 620 and 626 are moved in the axial direction by the hydraulic actuators 623 and 630 to adjust the groove widths of the V-grooves 622 and 628 of the pulleys 608 and 610. As a result, the winding radiuses of the transmission belt 612 on the pulleys 608 and 610 are continuously varied and a gear ratio of the belt-type continuously variable transmission 600 is continuously varied.
FIG. 17 is an enlarged cross-sectional view of the vicinity of the input shaft 604 and the movable sheave 620 enlarged in the primary pulley 608 of FIG. 16. As depicted in FIG. 17, an inner circumferential portion of the movable sheave 620 of the primary pulley 608 has a seal portion 632 formed on the side of the transmission belt 612 in the axial direction and has a female spline 634 formed on the side opposite to the transmission belt 612, i.e., on the side of the hydraulic actuator 623, in the axial direction. A torque transmitting portion 636 is formed that transmits torque when a male spline 635 of the input shaft 604 and the female spline 634 of the movable sheave 620 are spline-fitted, and an oil passage portion 640 is formed for supplying operating oil to an oil pressure chamber 638 of the hydraulic actuator 623.